Temperature measuring apparatus



I 'Oct.'19,"1 937. w. H. GILL E 7 TEMPERATH RE MEASURING APPARATUS FiledOct. 31, 1935 umomoowm mob/$52.

Jm On T ViZZw H. @1128 to decrease the rapidity with which v ,turemeasuring' apparatus oi the broad type wherein' the light givenr rr from"a hot body is used asan indication of the temperature thereof.

5 Devices of this kind have been devised wherein oneor'morejahoto-electric-ceils are subjected to the light from the hotfbody andtothe light from a separate sourceusuall'y-an electric lamp. Some. =of;these devicesemploy a principle of operation 2' which dependsuponi'acertain balance being maintained in the lightf furnished by the two Isources and in which, upon such a baiance'being destroyed :by reasonofthe temperature of the temperature measuring devices are remarkably,-

freefrom voltage v'ariations and give a fairly accurateii reading of thetemperature of the hot f body; iAllfof the devices of i this type,however,

shame; m'on'e" type or such devices, two photo:

7 electriccells are employed;'one of which is-illumi- Qnatedbyithehotbody-and the othe r c which is v illuminated by thel'amp, The dimcultWlth such a devicefis'that the use of two photowelectric cells Irendersthe apparatus; accurate ,nly when the r s ,response of the twophoto-ele'ctric'cells remains I unchanged: There is no assurance,however,

35 that' 'such a condition cane. maintained.

' i ln another type of su'ch devices, the difllculty of the-*previoustypei'is avoided by the use of only on'e' "photoelectricflcell and meansto alter- 49 from the hot {body :an'd light "from the lamp. ,Whiie sucha device avoids the objection tothe 1 on'e employing two photo-electriccells,'it is not Y Y s entirely satisfactoryin that thefmeans employed'toficontrol ithe-lamp' in response'to thev variation in balancebetweenthe twolightsources are not entirely satisfactory. In somecases such 7means involve theuse of a large number of moving mechanical parts whi chintroduce the 'pos-' sibility of error arising from wear and which tendresponds-tea changed condition;

I {An object of the present invention is tapro- "yide atemperaturemeasuringdevice of the type describedwhichunecessitates the use of onlyone I 55 photo eiectric cell and in whichthe; use of any the devicehavehad defectswhich render their use less/de- Inately s'ubjectYs'aidphoto electric cell to light L I 'rnsrrnnamnnsmAsUamo-aerana'ros 7 H 1f; P ul, M nama Min- J eavens-Honeywell Regulator Compmm'mn- J Minn, 'a.corpcration'of llltlicatienjoctober s1, lass, Serial: ea sues fascism"(ctzss 1,5

- M; invention ru tenbpnsw-memc temperamechanical elements sm enacments;

avoided. v a further object of my invention is to provide a new andnovel means for varying the current flow through acircuit inEaccor'dance'withthe variation in phase and magnitudeofthe musetions of apuisatingcurrent flowing in another circuit. I C l Oth'erobjectsof'myinventionwili be apparent from the consideration of theaccompanying spec- I 10 iflcation, claims an'ddrawing. cl Referring tothe drawing, my apparatus generally comprises a photo-electric cell IIIwhich is aiternatelysubjected to light from a hot body ll whosetemperature is to be measured, and

from an electric lamp II, through the action ofa rotated segmented disci8 driven by .a synchronous motor. The pulsating currentflowingthr'oughphoto-electric' cell 10 is amplified bymeans of a.thermionic amplifier l5 and con- 0 verted into alternating currentthrough a transformer I 6. This alternatingcurrent is applied tothegri'ds of two thermionicampliflers i1 and i8 which are oppositelyconnected in an output circult energized by the secondary of atransformer I9. Since the potential applied to said tubes is analternating one, and since the tubes are oppositely connected in saidcircuit, currentswill flow-throughone of said tubes in one-half cycleand through the-other in the other half cycle. 30

current flowing in the output circuit of tubes i1 and II will be analternating current, the positive peaks of which are controlled bytheintensity of the lightsupplied from one of the two sources of lightandthe negative peaks of which will be controlled by the light suppliedfrom the other source of light. The difference between the negative andpositive portions otthe alternating current, if any, is impressed 'upon,the input cirecult of a thermionic amplifler'tube so as to varythe'current flow through the output circuit of said tube depending uponwhether said difference is positive or negative. In the plate circuit ofsaid tube are indicating and recording means and a lamp 12. The phaserelation of the current flowing through the various portions of myapparatus is so controlled that in the event that the temperature of thehot body increases the flow of current inthe output circuit of tube 20also increases with a resultantincrease in the flow of current throughthe indicating andree cording means and through lamp l2,'thus tending tore-establish a balance between the light.

supplied from lamp l2 and from hot body ll.

Referring more particularly" to the details ;-'of my apparatus, I haveshown hot body .lifas located in a furnace 2|, which may be'of anysuit-'- able type for creating high temperatures. The

" segmented disc i3 comprises four segments spaced apart to provide gapstherebetween corresponding in width to the segments. As will be.

more or less obvious from the drawing,when' the disc *is in the positionshown, therein thelight from lamp l2 will be reflected onto thephotoelectric cell It. -When the disc is moved 45, however, thephoto-electric cell will be subject to the light from thehot body H. a nI v a The'synchronousmotor l4 driving said segmenteddisc l3 isof anysuitable type wherein it is possible to control the half cycle on whichthe motor will start. The motor-is connected through conductors "withline-wires 26, which supply into direct current.

are connected to a suitable'source of altemating' current. =1 1 Theamplifier tubes is and aresupplied with directcurrent through'aconventional powerf-supply- 25. which mayilbe of any: suitable form; for

convertingthe alternating current .of the power Said power supply. isconnected tothe line wires26 through conductors 21.; Said power supplyis; provided,with

various taps 28, 29, 30, 3| and 32, the potentials of which decrease inthe order named.

" The thermionic-amplifier ills shown in th form of a conventionalthreeselectrode vacuum tube in which the cathode is indirectly heated.

. Saidtube l5 comprises a cathode 22, a grid 23 and a plate 24..Thecathode22 oitube I5 is connected through aconductor33 with the tap30 of, the power supply unit, while the plate 24 isconnectedthrough'conductorsf34, 35 and to the positive terminal 28 of saidpowersupply.

in series with the primary 3! of transformer li. The plate circuit oftube i5 accordingly'comprises cathode 22, conductor 33; the portion ofthe powersupply' unit between taps .33 and 23,

conductors 33, 35, the plate '24. Y

primary, conductor 34 and One terminal ofphoto-electricicell I0 isconnected through conductor 38- to tap 23 ofthe power supply. The otherterminal of said cell is connectedthrough conductor 39 with oneterminalof a resistance .element 43. The other terminal of saidresistance element is connected- I to the negative terminal 320i thepower supply.

Thus, the photo-electric cell has a voltage sup-' ply theretocorresponding to the voltagebetween tap in and terminal- 32 and theoutput of'said cell is supplied to the resistance", which acts asacoupling resistance between the photo-cell, and tube It. Grid 23 isconnected to one-ten minal of said resistance through 'a condenser 4iwhich servesto; prevent the pas a e of any di rect current. A'resistance42 is connected .at one end between said grid 23 and condenser 4| andatthe other end to the tap .-3l ofthe power supply unit. Theconnectionaflorded by said resistance serves to bias the grid negativelywith i respect to the cathode.

previously stated,

tube 22. This transformer in addition to priman 31 comprises twosecondaries 43 and 44.

Amplifiers ll and'll are each shown in the" form of a threeelectrode"vacuumitube'of the in- P directly heated cathode type. Tube" comprises acathode 43, a grid 43 and a plate 41 The caththeprimary 31 oftransformer I6 is connected in the plate circuit of p and cathode oftube I'Lwhile the opposite terminals of secondary 44 are connected tothe grid] and cathode of tube 13. --,In'each case, such connection ismade through the biasing unit 43; I

The transformer I3 is employedto supply the .plate potential for. tubes"I! and" and heating current for all of t the .tubesemployedgThistransformer comprises aline voltage, a-prim'ary 49, a highvoltagesecondary i0. and raplurality v of .low voltage secondariesii which'furnish current for heating thecathode. heaters of the var- I iousvacuum tubes employed, The primary, 49' ofsaid transformer is connectedthrough conductors 52 withline wires 26. Oneterminal of'the secondary toisconnected through oonductors 53 and 54 with aconductor.

55, which connects the plate of tube l1 with the cathode of tube I3. Theother terminal of. saidsecondary is connected througha conductor Si aresistance, and a conductor 53 witha conducf tor 59 which connectsthecathodeof tubeil with r 1 a plate of tube ll. It willbe seen thatzthetwo I V tubes are: oppositely connected in a circuit energized by thesecondary 50 and including a. re sistance 51. :It will further beseenthat upon one-half cycle of the alternating voltage supplied by thetransformerv l9, one' ofthe tubeswill con duct current due to oneplatebeingmore posiI-f tive than thecathode and on the other half cyclethe. other tube will conduct current. Thus an alternating current: willflow in the output circult of these tubes, the current in one-half-cycle' being. controlled by one of the tubes and the curtrent in,the; other half cycle beingcontrol'led by the other-one thereof. 0A.condenser .30 is-connected across the termina1s of,resistance 51 and isof sufiiciently large capacity to bypass the majorityof the'alternatingcomponent of the current flowing in said circuit. Thus, there will be avoltage drop acrossresistance 51 onlywhen the positive and negativeportions of the current difler inmagnitude, resulting in ponent. w -.Theamplifier 23 issimilarlya conventional three-electrode vacuum tube Vcomprising an indirectly heated cathode BI, a grid62 and a plate j 63.Cathode is connected through a conductor 65 64 and conductor 33 with atap 30 of the power supply. ,Grid 32 is connected through a conductorGLresIstanceBI, conductor 56,;conductor 66 a direct current cornwith thenegative terminal 32 of the power supply I unit. Thus,when there is novoltage drop'across resistance '5'! the grid 32 is biasednegatively by avoltage equivalent to the voltage drop between taps 30' and 32. In theevent, however of a volt age drop in either direction in the resistance5.1.

the grid bias will obviously be changed.

The plate 63 of tube 23 is connected through a and conductors H- andwith the positive ter- 28 ofthe powersupply unit. Since the I cathodeiiis connected as previouslyexplained to tap 30, the plate circuit of tubeI! will have a voltagecorresponding to that between taps 2| andIll'impressed thereon. The plate circuit,

moreover, includes lamp l2 and indicators 68 and I! so that" any changein flow 01! current due to I plate" circuit will cause acorrespondingchange in flow of; current through these devices. I

' long as the ll'ghtfromthe hot body H I through the platecircuit otsaid tube -'will be a direct non-pulsating current with the result'thatno voltage will be produced'in secondaries l3 and i thefevnt, however-,that the temperature of" the hotibody If either rises or falls so thatthe light received therefrom by the photo-elec- -trio cell ill becomesmore or less than 'the light received from lamp l2; the current flowingthrough photo-electric cell ID will become pulsat- :ing in characteapdueto the-fact that the resistance" thereof" isless when subjected to oneof said sources oi. .light'than when 'it" is "subject-4 ed 'to theother. This pulsation in'thecurrent will cause a pulsating voltage to beapplied to I grid 23 causing the'plate current of tube II to bepulsating. The flow'of this pulsating current through the primary 31 oftransformer ll produces an alternating voltage in secondaries 43 and 44,which alternating voltage is applied to thegrids of tubes "l1 and it. Aspreviously ex-' plainedythe frequency ofthe pulsating current is sorelated to the frequency of the alternating current suppliedbytransiormer "that for each pulsation there is a corresponding halfcycle of alternating current. Further, as previously explained-Jon once!said half cycles one of thetubes l1: and 18 passes current and on theother one-half cycle the other tube passes current.

-' the grids by the secondary 42 the result will be when an alternatingcurrentis impressed upon that on one-half cyclethe two grids bepositiveand onthe other half cycle" the two grids will'be negativewith're'spect to the respective 'cathodes. Thus, the currentflowthrough' the tube which occursat the time that the grids arepositive will be relatively large, while the current flow which occursthrough the other tube while the grids are negative will be relativelysmall. "The result will be that the current in the portion of the outputcircuit including the resistance 51 and the condenser" will be analternating current; the positive and negative portions of nent of thiscurrent passes for the most part through condenser 60 due'to therelatively low impedance thereof tosaid alternating component,. while*the directcomponent thereof flows through resistance 51. .The resultwill-be that there will be a voltage drop across resistance 51 thepolarity of which depends on whether the positive or negative halves ofthe current in the and: irom the lamp I 2 is of equal intensity. thecur-- I rent' flowing through the photo-electric cell V I wili' besubstantially non pulsating. Due to the; blocking actionoicondenser' ll,the gridbias of output'circuits of tubes l1 and [8 are greater.Since'resistance is in the grid circuit of tube 20,- any voltage dropacross the same affects the,

bias of said tube, as previously explained. A change in this bias causesa corresponding change in the flow oi plate current of said tube and duetothe fact that the lamp i2 and the recorder 68 and'indicator 68 are insaid circuit such a change will cause a change in theflow of currentthrough these devices. It will be readily seen that by properly timingthe start of the synchronous motor M with respect to the phase of thealternating current of the power supply, it is possible to cause anincrease in the temperature of body II with the resultant increase inthe light supplied to the photo-electric cell to by said. body to resultin an increase in the flow of current through lamp l2. When this is thecase, any unbalancing of the system caused by the temperature oi the hotbody changing will immediately affect the flow of currentthrough lamp l2in a direction tending to re-balance the system. This change in flow ofcurrent also serves as a means forindieating and recordingthetemperature oi the 'hot power supply, the only direct .efiect thereofwould be a change in the illumination of lamp l2. Thus, if the linevoltage should decrease, the current through lamp l2 would decrease dueto a decrease in. the'varlous voltages applied to the tubes. Upon such adecrease in current flow through lamp i 2 taking place, however, thesystem is unbalanced' and lamp I2 is supplied with more current inprecisely the same manner as previously described. Such an increase inthe current flow through lamp l2 tends to restore sa d current flow tothe value it had before such voltage fluctuationtook place. Thus, mytemperature measuring. device gives an accurate reading even thoughthere bea large variation in the voltage of. the power supply.

It will beseen that aside from the synchronous motor, my apparatusinvolves the use of no moving parts whatever. All of the action takingplace rom thetime the circuit is unbalanced due to the photo-electriccell receiving more light from one oi the two sources of light than fromthe other occurs through the medium of thermionicdevices, the response.of which, as is well known, is almost instantaneous. Thus, in the event01" any change occurring in my apparatus due to a change in the hot bodyIt or due to a change inthe line voltage, the apparatus willinstantaneously respond to such change and will assume a new balancedcondition,

While I have shown a specific embodiment of my device, it will beunderstood that this is for purposes of illustration only, and thatmy'invention is limited only by the scope of the appended claims. a

-I claim as my invention: 1. In apparatusfor use with a source of light,an electric lamp constituting a second source ot light, a lightsensitive cell, means for alternately subjecting said photo-electriccell to light from said source and from said lamp, an amplifiercomprising a space discharge device, an output circuit for said spacedischarge device includingsaid electric lamp and current translatingmeans, means for energizing said circuit, an input circuit'tor saidspace discharge device, and means associated with said input circuit,operative upon said light sensitive cell receiving more light from oneof said sources of light than Pillmeans for applying a voltage to thegrids of said valves which varies inaccordanc'e with said pulsating.'current,said valves being connectedop- 'positely in a common outputcircuit, and means in said circuit for alternately applying apotential teach'valve of, a polarity causing'the same to pass current; said meansalternately applying" saidpo- 'tential with a frequency corresponding tothe i're- -q'uencyfoi the pulsating current.

9. In combination, a first circuit, an amplifier "comprising a spacedischarge device, an output 15. it direct voltage-for energizing saidoutput circuit,

circuit for said space discharge device, a source of I aninput-circuittor said space discharge device,

I 1 means forirnpressing-a normally substantially constant biasingvoltage on said input circuitto maintain a normally substantiallyconstant flow 1 or direct current in said output circuit, and physicallystationary means operative upon the pres- 'ence of a pulsating directcurrent in said first circult to cause said biasing voltage to assume anew substantially constant value, the magnitude 01' a L which isdependent upon the magnitude and phase f 1 so position" otthealternating component oi'asaid pulsatingcurrent. a 10, In combination, afirst circuit, an amplifier comprising'a space discharge device, anoutput circuitior said space discharge device, a source of directvoltage for energizing said output circuit,

an input circuit for said space discharge device, a means, forimpressing a normally substantially biasing constant voltage on saidinput circuit to I maintain a normallysubstantially constant flow ofdirect current in saidoutput circuit, physically gstationarymeansoperative-upon the presence of I a pulsating dire'ct current insaid first circuit to cause saidbiasing voltage to assume a newsubstantialiy constant value, the magnitude of which is dependent uponthe magnitude and phase position of the alternating component of saidpulsating current, said means comprising a plurality or gridcontrolledspace discharge valves, means for applying a voltage to thegrids of said valves which varies in accordance with' the alternatingcomponent of said pulsating current, said valvesb eing'connectedoppositely in a common output circuit, and means in said common outputcircuit for alternately" applying a potential to I each valve of apolarity causing the same to pass current,'said' meansalternatelyapplying said p0- ,te ntialsgwith a frequency corresponding to thefrequency of the'pulsating current, and physically stationary means, forvarying'the biasing voltage I applied to the input circuit of saidamplifier space discharge device in accordance with the value of apulsating direct current flows the direct current component of thecurrent in said common output circuit.

11. In combination, a first circuit, an amplifier comprising a spacedischarge device, an output circuit for said space discharge device, asource of direct voltage for energizing said output circuit, an inputcircuit forsaid space discharge de-'- vice, means for impressing anormally substantially constant biasing voltage on said inputcirculttofmaintain a normally substantially constant flow of direct current insaid output circuit,

. physically stationary means operative upon the presence of a pulsatingdirect current in said first circuit to cause said biasing voltage toassume a newsubstantially constant value, the magnitude of which isdependent upon the magnitude and phase position. of the alternatingcomponent oi.

said pulsating current, said means comprising a plurality of gridcontrolled space discharge valves,

means for applying a voltage to the grids 01' said valves which variesin accordance with the alternating component 01' said pulsating current,said valves being connected oppositely in a common output circuit,meansin said common output circuit for alternately applying a potentialto each rent, said means alternately applying said po- 7 tentialswith afrequency corresponding to the frequency of the pulsating current, andmeans consisting of a resistance and a by-pass condenser paralleltherewith connected in both said common output circuit and saidamplifier input circuit.

12. In combination, a first circuit, means for inducing in said circuitthe flow 01' a direct current, a condition responsive device in saidcircuit, means for periodically and successively subjecting saidcondition responsive device to each 01' two conditions tending to afiectthe conductivity of said element so that upon said conditions havingvalues such, as to afiect said device unequally,

through said circuit, an amplifier comprising a space discharge device,an output circuit for said space discharge device, a source of directvoltage for energizing said output circuit, an input circuit for saidspace discharge device, means for impressing a normally" substantiallyconstant biasing voltage on said inputcircuit to maintain a normallysubstantially constant flow of direct current in said output circuit,and physically stationary means operative uponthe presence of apulsating direct current in said first circuit to cause said biasingvoltage to assume a new substantially constant value, the magnitude ofwhich is dependent upon the magnitude and phase position of thealterpulsating current.

valve oi a polarity causing the same to pass cur-

